A comparative study of the solvent extraction of vanadium(V) from hydrochloric acid and sodium hydroxide media was separately carried out using Aliquat-336 (methyltrioctylammonium chloride) extractant dissolved in kerosene containing 10% n-octanol as phase modifier. The different parameters affecting the extraction process including acid, alkali, extractant, metal concentrations, phase ratio and loading capacity as well as the temperature were separately investigated. Vanadium(V) species were suggested to be (H(2)V(10)O(28))(4-) and (VO(3)O(H))(2-) in acidic and alkaline solutions, respectively. Based on the obtained results, the extraction equilibria were deduced and the optimum conditions for the extraction of vanadium were proposed. The method was applied for treatment of the spent catalyst used in the manufacture of sulphuric acid industry giving a recovery of 93.0% for vanadium in the whole process. (C) 2009 Elsevier B.V. All rights reserved.